- SCIRT Standard Details
SCIRT standard details were developed to ensure a consistent approach to common design elements, and to save design time by providing a quick reference to an agreed standard design rather than creating new design drawings of the same element. For example, a standard drawing for a water supply backflow preventer.
Standard details also clarified the requirements of the Infrastructure Recovery Technical Standards and Guidelines (IRTSG) and the Construction Standard Specification (CSS), for example when the information was out of date.
Standard details were required because SCIRT's four design teams had different approaches, potentially resulting in variation in the design outputs and confusion for Delivery Teams and sub-contractors.
Standard details were developed within the Technical Groups in consultation with:
- Design Teams
- Estimating Teams
- Delivery Teams
- Asset Owners
- Asset Owners' Maintenance Team representatives
- Technical Leads
The benefits of standard details included improved quality of construction through consistency of requirement, cost savings through reduced design and construction time, and more efficient operation and maintenance as details were standard across the network.
Once each standard detail was developed and approved by the Technical Leads, it was uploaded to Project Centre where it was available to both Design and Delivery Teams.
A reference index for SCIRT standard details and CSS details was compiled In order to clarify where conflicts existed between the two and where SCIRT standard details took precedence.
Many of the SCIRT developed standard details were adopted by the Christchurch City Council, and included in later versions of their CSS.
- Pipe Profilometer and Design Guideline
A guideline to inform designers of the pipe profilometer operation, including requesting profile surveys, standards, and the assessment of the survey results.
Inspection of the gravity wastewater pipes was typically undertaken by Closed Circuit Television (CCTV).
However, one limitation of CCTV was its relative inability to accurately quantify pipe dips with the precision demanded by the Council or Industry Specifications.
The pipe profilometer programme for measuring dips in gravity wastewater pipes was an innovative use of technology from the geotechnical engineering industry for assessing the amount of vertical pipe movement in areas that had experienced significant differential settlement.
A trial was undertaken of different profile measuring technologies and the one found most suitable was Geotechnics Ltd's "profilometer", typically inspecting to an accuracy of +/- 5mm. Launched and controlled from a custom built twin axle trailer, the profilometer crew and traffic management requirements were similar to that for CCTV.
The Geotechnics Pipe Monitoring Team created their own trailer from which to run their profilometer operation, and won a Bill Perry safety award in recognition for the number of safety hazards the trailer eliminated: http://strongerchristchurch.govt.nz/article/underground-investigators-break-new-ground-in-health-and-safety-design
A profilometer, or level sonde, was pulled through the pipe (typically from a downstream manhole to an upstream manhole), recording the elevation of the sonde in relation to a base station at specified intervals, typically one metre. The resulting graph, or "profile", was shown as a pipe longsection displaying pipe inverts at 1 m intervals.
A Designer Guideline was created to inform SCIRT designers of the operation and how to interpret and use its outputs within the design framework of the Infrastructure Rebuild Technical Standard and Guidelines (IRTSG).
- Profilometer: a level sonde that is pulled through the pipe (typically from a downstream manhole to an upstream manhole), recording the elevation of the sonde in relation to a base station at specified intervals, typically one metre.
- CCTV: Closed Circuit Television.
- Huntsbury Reservoir
Among Christchurch's most hard-hit earthquake-damaged facilities was the Huntsbury Reservoir. Water drained from the shattered 35,000-cubic-metre storage basin, the city's principal drinking water storage facility. Innovative design and prompt decision-making proved paramount in the rebuild process.
At 12.51 pm on February 22, 2011, a high-intensity earthquake emanating from under the Port Hills of Christchurch pounded the city.
Across the dry slopes, the damage was immense as the reverberations were felt far and wide. Among the most hard-hit was the all-important Huntsbury Reservoir. Water drained from the shattered 35,000-cubic-metre storage basin, disappearing into the cracked hills.
Ongoing tremors further fractured the city's principal drinking water storage facility.
Built in 1952, the reservoir was badly battered. A reinforced concrete structure - measuring 77.4 metres by 63m - with a 7.25m water depth, the roof was overlaid with soil and grassed, and the walls ranged from fully buried to exposed, cut into a sloping site.
Responsibility for much of the damage lay with an undiscovered "shear zone" under the reservoir. As a result, not only was the main storage facility out of operation, there was extensive damage to the pump station.
Complicating repairs was the shear zone. Geological probes utilised boreholes to confirm the surprise find. An inspection of the borehole material revealed interfaces where rock-to-rock faces had slid across each other. It was estimated that the last shear zone movement occurred 15,000 years ago.
To accommodate future shear zone movement, structural changes were needed.
Two trapezoidal plan-shaped reservoirs were built either side of the shear zone.
A floor slab was overlaid on the existing slab and a reinforced concrete foundation and walls adjacent to the shear zone were built, along with a reinforced concrete roof.
The existing perimeter walls remained, while the roof column supports were reused.
The roof slab was designed to allow a crane to operate on the surface during construction. It was overlaid with a fibreglass-reinforced PVC sheet membrane.
Under the pump
In a paper on post-earthquake work on the reservoir, contractors Beca and Fulton Hogan and the Christchurch City Council detailed the damage, including "a broken inlet/outlet pipe flanged connection, extensive dislocation and cracking of floor slabs, cracking of the roof slab and some movement at wall joints adjacent to the corners of the structure".
However, the associated pump station was "damaged beyond repair".
Filling the void
A nearby inspection revealed other issues. The inlet/outlet pipe traversed an adjacent road, Huntsbury Avenue, via a tunnel. A tunnel check revealed collapsed roof sections.
The inlet/outlet pipe proved to be intact. The void between the pipe and the tunnel was filled with foam concrete, protecting the pipe from any falling roof material and cushioning it from further movement.
The restricted site access, confined space, tunnel debris hazards and the risk of future earthquakes influenced the rebuild decision.
Stage one of the reservoir and a new pump station were commissioned in December 2011, allowing water to be pumped to areas above the zone served by the reservoir. Stage two was commissioned in November 2012.
Teamwork, prompt decision-making, astute risk assessment and community consultation were key elements in the success of the project. However, the need for reservoir resilience and the attention to design details were paramount.
Huntsbury Reservoir repairs timelapse: https://www.youtube.com/watch?v=pmOh_Uyf5j4
Where has all Huntsbury's water gone? News story: https://www.youtube.com/watch?v=swVrPNB4q8o
- Liquefaction Trial Report
The challenges of rebuilding underground infrastructure in liquefaction-prone Christchurch were put under the microscope in a controlled field assessment of the performance of below ground infrastructure in simulated liquefied soils.
The Liquefaction Trial was carried out after the Canterbury Earthquake Sequence (CES) of 2010-2011 prompted the Christchurch City Council (CCC) to amend infrastructure design standards to incorporate more conservative detailing aimed at providing greater seismic resilience. Changes were made to pipe and chamber material selection, design detailing, and backfill material type.
In the trial, a range of pipes, chambers and backfill materials were assessed. Liquefaction was triggered within the soils through a sequenced detonation of explosives within an array of boreholes.
A report covered the findings and interpretations from the trial, and discussed the current theory around the performance of buried infrastructure during liquefaction events.
The trial provided evidence to support the resilient design solutions incorporated into the SCIRT rebuild, which were found to be pragmatic and practical, exhibiting an appropriate level of resilience and optimised value. The standard details used by SCIRT were appropriate for most conditions in Christchurch and other areas which showed susceptibility to liquefaction.
- Asset Owner's Representatives and Technical Leads
Asset Owner's Representatives and Technical Leads from the New Zealand Transport Agency and Christchurch City Council were co-located with the team at SCIRT's central office. There were one or two Asset Owner's Representatives and Technical Leads per asset type. Their role was to provide an Asset Owner's perspective to the rebuild of the city's infrastructure.
Asset Owner's Representatives worked closely with the Project Definition, Asset Assessment and Design teams to assist with developing SCIRT's scope of work in accordance with the Asset Owner's standards and guidelines.
Technical Leads worked as technical advisors with Design teams through the detailed design and construction phases of projects.
Some of the benefits from having Asset Owner's Representatives and Technical Leads as part of a co-located team included:
- Providing expert, hands-on, in-depth, historical knowledge of the assets and their management, including technical understanding.
- Fast, expert advice to assist with trouble shooting and issues arising.
- Assisting designers to understand special circumstances, risk and issues likely to affect design and construction.
- Supply of expert knowledge of Asset Owner's systems, policies and procedures.
- Bridging the gap - providing a single point of contact for the SCIRT team with the Asset Owners, and business as usual asset maintenance teams.
- Providing an Asset Owner's strategic, whole-of-network viewpoint and advocacy and an understanding of the impacts of decisions on related assets. This included whole-of-life considerations, funding implications, and developing innovations.
- Providing Asset Owners with confidence in decision making.
- Enabling faster, better informed decision-making and technical assistance, resulting in expedited workflow.
- 12d - One-Stop-Shop Design Tool
12d Model was the terrain modelling, surveying and civil engineering software package selected for design at SCIRT.
12d Model's field-to-finish capability meant only one design package was needed, enabling a streamlined approach through survey, design and as-builting phases.
SCIRT's design team developed tailored 12d tools to enable increased efficiencies when modelling and designing wastewater, water reticulation, storm water and roading projects.
At its peak, SCIRT had 176 designers from more than 20 different consultancies. All needed to learn how to use 12d quickly, and needed to use it consistently. A 12d training programme was created for this purpose, enabling designers to gain basic 12d operating skills within exceptionally short timeframes.
The zip file below contains the suite of SCIRT's 12d training manuals and files.
SCIRT's 12d team presented at bi-annually at the 12d Model International User Conference. The videos of these presentations are available on YouTube:
- 12d Model International User Conference 2012: https://www.youtube.com/watch?v=luXZyk7Aobo
- 12d Model International User Conference 2014: https://www.youtube.com/watch?v=MT-wTdptDRk
- 12d International Conference 2016: https://www.youtube.com/watch?v=GrlLiwKpQ4c
The 12d team also presented at the International Federation of Surveyors Working Week in 2016: https://www.youtube.com/watch?v=3WXxe3HNC5A
- Refurbishment of Gabion Walls with Anchors - a Trial
SCIRT proposed that damaged gabion retaining walls could be refurbished by installing anchors through the existing baskets, secured into the ground behind them. This could provide a cost and time saving because baskets would not need to be removed or replaced and, therefore, significant volumes of excavation and backfill work could be avoided with resulting reduced construction time. In order to establish if this solution was feasible, two test anchors were installed by Rock Control in March 2014 to determine if the process was practical and was an efficient means to refurbish such walls.
The following observations were made:
- Drilling of the anchors was possible and while the mesh at the rear of the basket was awkward to penetrate, it could be done.
- During grouting there was no grout recovery and, therefore, uncertainty regarding the completeness of the grout penetration. This meant all anchors had to be load tested.
- Galvanising and sacrificial steel were the only corrosion-protection measures for self-drilling anchors.
- The testing regime needed consideration because measuring deflection while holding load might prove challenging and required designer testing requirement approval.
- It was suggested that loads for anchor tests be derived for individual or zones of anchors to ensure the load was not excessive. This would require specific load definition, rather than simply applying the largest load for the whole wall and testing all anchors.
- The gabion baskets were damaged by the plate used in testing. Therefore, using a textile layer or other protection under the plate might be advisable. Alternatively, the basket might need to be patch repaired.
- Anchors should be installed in the middle of baskets to allow sufficient space for the pressure plate to span.
In conclusion, both the installation and testing of the trial anchors through gabion baskets were successfully completed. For the future implementation, it was recommended the above lessons be adopted into the design and specification for installing anchors through existing gabion baskets.
- Pipe Damage Assessment Tool (PDAT)
A pipe damage assessment tool (PDAT) was developed to give a risk based prediction of pipe condition to avoid the need for a CCTV survey of every pipe in the city.
With more than 2,500 km of storm water and wastewater pipes needing to be assessed for damage before design work could start, SCIRT needed to develop a fast, cost-effective way of determining pipe damage, without having to Closed-circuit Television (CCTV) survey every pipe.
SCIRT's Asset Assessment and GIS teams developed a pipe damage assessment tool (PDAT) that predicted the structural condition of pipes that were not CCTV surveyed.
The PDAT used a range of key damage indicators to predict pipe damage, including CCTV completed on other pipes in the area, pipe material and age and land damage indicators.
SCIRT found the PDAT accurately predicted the conclusions of a CCTV survey for 75% to 95% of the pipes in a catchment network based on CCTV samples of 5% to 30% of the total network.
- CCTV: Closed-circuit Television
- PDAT: Pipe Damage Assessment Tool
- RAMM: Road Assessment and Maintenance Management (software)
- LPI: Liquefaction Potential Index (assesses the damage potential of liquefaction)